Thermal decomposition of 2,2,6,6-tetramethyl-(1-phenethyloxy) piperidine

The thermal decomposition characteristics of 2,2,6,6-tetramethyl-1-(1-phene thyloxy) piperidine, a stable covalent adduct of a benzylic radical derived from ethylbenzene and a nitroxyl radical, 2,2,6,6-tetramethyl-1-piperidiny loxy have been studied using a variety of techniques. This adduct has been used to initiate the polymerization of styrene. The adduct decomposes therm ally to generate a benzylic radical capable of initiating polymerization an d a passive nitroxyl radical which reversibly forms a covalent bond with th e propagating chain end. Thus the polymerization proceeds under living cond itions. The thermal decomposition of the adduct has been examined in detail in an attempt to better understand the reversibility of chain capture duri ng polymerization. The adduct decomposes to form predominately styrene and a hydroxylamine corresponding to the nitroxyl fragment. Small amounts of 2, 3-diphenylbutane and ethylbenzene are also formed. The activation energy fo r the decomposition, which reflects the cleavage of the nitrogen-oxygen bon d, is 30.6 kcal/mol. (C) 1999 Elsevier Science B.V. All rights reserved.